This invention relates in general to actuator mechanism and in particular to an improved electrical actuation mechanism adapted for use in a vehicle disc brake assembly.
Electric motors are convenient and well known devices for converting electrical power into motion. The rotary motion produced by electric motors can be converted into a linear motion, which is more useful in certain situations, in a number of ways. One actuator device which is known for converting rotary motion into linear motion is the spindle gear mechanism disclosed in U.S. Pat. No. 4,926,708 to Dietrich et al, the disclosure of which is incorporated by reference herein.
Most vehicles are equipped with a brake system for retarding or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are actuated by hydraulic, pneumatic, or electrical mechanisms when an operator of the vehicle depresses a brake pedal.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. A caliper assembly is slidably supported by pins secured to an anchor plate. The anchor plate is secured to a non-rotatable component of the vehicle, such as the steering knuckle in a front wheel drive vehicle. The caliper assembly includes a pair of brake shoes which are disposed on opposite sides of the rotor. The brake shoes are operatively connected to one or more hydraulically, pneumatically, or electrically actuated pistons for movement between a non-braking position, wherein they are spaced apart from opposed axial sides or braking surfaces of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed braking surfaces of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the opposed braking surfaces of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.